Controlling the memory buffers used by a messaging engine

Use this task to control the sizes of the memory buffers used by a messaging engine.

About this task

Every messaging engine manages two memory buffers that contain messages and message-related data. You can set the following properties to improve the interaction of a messaging engine with its data store.
Name Value
sib.msgstore.discardableDataBufferSize The size in bytes of the data buffer used by the messaging engine to contain data for which the quality of service attribute is best effort nonpersistent. The messaging engine holds this data entirely within this memory buffer and never writes this data to the data store. When the messaging engine adds data to this buffer, for example when the messaging engine receives a best effort nonpersistent message from a client, the messaging engine might discard data already in the buffer to make space. This behavior enables the messaging engine to discard best effort nonpersistent messages.

The discardable data buffer contains all data for which the quality of service attribute is best effort nonpersistent. That data comprises data both that is involved in active transactions, and any other best effort nonpersistent that the messaging engine has neither discarded nor consumed. The messaging engine can discard only data that is not involved in active transactions.

Tip: If the messaging engine attempts to add data to the discardable data buffer when insufficient space remains after discarding all the data that is not involved in active transaction, the messaging engine throws a com.ibm.ws.sib.msgstore.OutOfCacheSpace exception. Client applications can catch this exception, wrapped inside API-specific exceptions such as javax.jms.JMSException.

The sib.msgstore.discardableDataBufferSize property of the messaging engine controls the size of the discardable data buffer. You specify the value of this property in bytes. The default value is 320000, which is approximately 320 kilobytes.

sib.msgstore.cachedDataBufferSize The size in bytes of the data buffer used by the messaging engine to contain data for which the quality of service attribute is better than best effort nonpersistent and which is held in the data store. The purpose of the cached data buffer is to optimize the performance of the messaging engine by caching in memory the data that the messaging engine might otherwise need to read from the data store. As it writes data to the data store and reads from the data store, the messaging engine attempts to add that data to the cached data buffer. The messaging engine might discard data already in the buffer to make space.

The sib.msgstore.cachedDataBufferSize property of the messaging engine controls the size of the cached data buffer. You specify the value of this property in bytes. The default value is 320000, which is approximately 320 kilobytes.

sib.msgstore.transactionSendLimit The maximum number of operations that the messaging engine includes in each transaction. For example, each JMS send or receive is an operation that counts towards the transaction send limit. The default value is 100.
Attention: The messaging engine uses approximate calculations to manage the data it holds in the memory buffers. Neither of the DataBufferSize properties gives an accurate indication of the amount of memory that the messaging engine consumes in the JVM heap. The messaging engine can consume considerably more heap storage than the DataBufferSize properties indicate.

To set the properties of a messaging engine to improve its interaction with its data store, use the administrative console to complete the following steps:

Procedure

  1. In the navigation pane, click Service integration > Buses > [Content Pane] bus_name > [Topology] Messaging engines > engine_name > [Additional Properties] Custom properties .
  2. Type the name of the property that you want to set.
  3. Type the value that you want to set for that property.
  4. Click OK.
  5. Save your changes to the master configuration.

What to do next

Remember: When you change any of these properties, the new values do not take effect until you restart the messaging engine.



In this information ...


Related concepts

IBM Redbooks, demos, education, and more

(Index)

Use IBM Suggests to retrieve related content from ibm.com and beyond, identified for your convenience.

This feature requires Internet access.

Task topic    

Terms of Use | Feedback

Last updated: Sep 20, 2010 11:08:29 PM CDT
http://www14.software.ibm.com/webapp/wsbroker/redirect?version=vela&product=was-nd-mp&topic=tjm0220
File name: tjm0220_.html